Oil extraction process and apparatus therefor

ABSTRACT

A process for solvent extraction of oils, in an extraction chamber, comprises the formation of a solvent mist with significant adiabatic cooling, whereby a pressure difference between the solvent inlet and outlet of the extraction chamber drives the solvent mist through the raw oil bearing. The solvent is fed to the extraction chamber at pressures exceeding atmospheric pressure, and the outlet of the extraction chamber is subject to a partial vacuum. An apparatus for solvent extraction comprises an extraction chamber for receiving oil bearing raw material therein, said extraction chamber comprising a solvent spray injection system connected via an inlet to a high pressure solvent feed circuit portion, said extraction chamber further connected via an outlet to a low pressure circuit portion connected to a gas recovery vacuum pump system.

[0001] This invention relates to a process for extracting oils and fatswith the use of a solvent.

[0002] This invention relates in particular, but not solely, to thesolvent-based extraction of essential oils from natural products. Manyplants, seeds and other natural products contain essential oils that canbe extracted using a solvent. A commonly used solvent for extraction ofoils from natural products is carbon dioxide, which is usually used inits super critical phase during extraction. This makes it necessary toprovide apparatus that can contain high pressures. The expense of carbondioxide extraction means that it can only typically be used forexpensive items or in high volume production, examples beingpharmaceuticals and instant coffee.

[0003] Other commonly used solvents for oil extraction are hydrocarbons,such as butane, isobutane and propane, for example as described in U.S.Pat. No. 1,802,533, U.S. Pat. No. 2,254,245, U.S. Pat. No. 5,041,245, EP812903, U.S. Pat. No. 5,980,964, and U.S. Pat. No. 6,225,483 B1.

[0004] In the extraction processes described in the aforementionedpublications, raw material is bathed or wetted with solvent for asufficiently long time to allow the oils and fats to be extracted todissolve in the solvent, or to form a miscella floating on the solvent,the solvent subsequently being removed by heating or by means of avacuum to boil off the solvent. The heating of the extracted solvent andoil mixture is disadvantageous since it destroys some of the qualitiesof the extracted oil, affecting for example its flavour, olfactoryprofile, vitamin content and other heat sensitive components.

[0005] Extraction processes as described in U.S. Pat. No. 2,254,245,U.S. Pat. No. 5,980,964 and U.S. Pat. No. 6,225,483 suggest the use ofcold solvents for extraction. The cold solvent however or raw material,is chilled by a cooling system, which is energy intensive and thereforefairly costly to operate.

[0006] A further disadvantage of known extraction processes is that theyuse large quantities of solvent. Process times are relatively high inview of the need to bathe the raw material in the solvent for a lengthyperiod of time, compounded by the need to subsequently remove thesolvent from the extracted oils and fats. It is also difficult withknown extraction methods to obtain very high yields of oils from rawmaterials without multiple extraction passes. Besides the time andexpense, subjecting material to multiple extraction runs, is not withoutadverse effects on the qualities of the extracted oil. The yield andolfactory profile of oils extracted from many plants is of greatimportance, particularly for plants with low oil content that areconsidered to be relatively rare.

[0007] It is an object of this invention to provide a process forextracting oils from oil bearing material, by solvent extraction, thatis effective and economical.

[0008] It would be advantageous to provide a process for solventextraction of oils and oil fats from plant material that produces highquality oils, in particular as concerns their flavour or olfactoryprofile.

[0009] It would be advantageous to provide a solvent extraction processthat produces high yields of oil from the starting material.

[0010] It would be advantageous to provide a solvent-based extractionprocess that uses low quantities of solvent.

[0011] It is a further object of this invention to provide an apparatusfor carrying out the solvent-based extraction processes mentioned above.

[0012] It would be advantageous to provide an apparatus forsolvent-based extraction that is economical and simple to operate.

[0013] Objects of this invention have been achieved by providing aprocess for solvent extraction of oils according to claim 1.

[0014] Disclosed herein is a process for extracting oils and oil fatsfrom oil and/or fat bearing raw material, comprising the formation of asolvent mist generting significant adiabatic cooling of oil bearingmaterial in an extraction chamber, whereby a pressure difference betweenan inlet and an outlet of the extraction chamber drives the mist throughthe oil bearing material, the pressure at the extraction chamber outletdropping below atmospheric pressure by action of a partial vacuum.

[0015] Also disclosed herein is an apparatus for solvent extractioncomprising an extraction chamber for receiving oil bearing materialtherein, said extraction chamber comprising a solvent spray injectionsystem connected via an inlet to a high pressure solvent feed circuitportion, said extraction chamber connected via an outlet to a lowpressure circuit portion connected to a gas recovery vacuum pump system.

[0016] Advantageously, the rapid freezing of oil bearing raw materialand the flow of a super critical mist through the frozen raw materialwashes the oils from the material in an effective and efficient manner.In particular, small quantities of solvent are used in comparison toconventional methods in which the raw material is soaked in solvent. Thelow solvent use significantly improves removal of solvent from extractedoils, and with the absence of heating, ensures extraction of oils withhigh olfactory and flavour profiles. Furthermore, the process isparticularly energy efficient, since no cooling of solvent or rawmaterial is required on the one hand, and, on the other hand, heating isnot required for solvent extraction.

[0017] Further objects and advantageous aspects of this invention areset forth in the claims or will become apparent from the followingdescription, with reference to the figures in which:

[0018]FIG. 1 is a simplified view of an apparatus for solvent extractionaccording to this invention;

[0019]FIG. 2a is a cross-sectional view through an extraction chamber ofan extraction apparatus according to this invention;

[0020]FIG. 2b is a perspective cross-sectional view of an upper part ofthe extraction chamber according to FIG. 2A;

[0021]FIG. 2c is a view from below of a top end of the extractionchamber of FIG. 2a, showing the solvent injection system;

[0022]FIG. 3a is a cross-sectional view of an oil collection chamber ofthe apparatus according to FIG. 1; and

[0023]FIG. 3b is a perspective cross-sectional view of the oilcollection chamber.

[0024] Referring to the figures, in particular FIG. 1, an oil extractionapparatus is shown comprising an extraction chamber 2, an oil collectionchamber 4, a solvent recovery pump system 6, a vacuum chamber 8, anoverpressure and condensation tank 10, and a solvent tank various tanksand chambers are interconnected by solvent circulation circuit 4comprising a high pressure circuit portion 17 and a low pressure circuitportion 15. The circuit comprises a number of conduits, pipes or othergas flow means, whereby the arrows indicate the principal direction offlow of solvent.

[0025] Referring to FIGS. 2a to 2 c, the extraction chamber 2 comprisesa casing 16 comprising upper and lower cover portions 18, 20 removablymounted at opposed ends of a central tubular portion 22 defining avolume therein for receiving an oil bearing material 24. The oil bearingmaterial 24 may be placed in the extraction chamber by removing the topcover portion 18 and packing in the material which rests on a sieve, forexample a removable perforated metal plate 26 seated at the bottom ofthe tubular portion 22 but spaced at a certain distance above the bottomcover portion 20. Depending on the type of raw material, the amount, andthe extraction process parameters such as pressure and solvent type, theoil bearing raw material may either be loosely packed in the collectionchamber or tightly packed, for example by tamping, using a ram orsimilar technique. The sieve 26 may be interchanged and adapted toretain the smallest particles of the oil bearing raw material.

[0026] The upper cover portion 18 comprises a solvent spray injectionsystem 28 comprising a plurality of spray nozzles 29 and a solventdistribution circuit 30 interconnecting the nozzles 29 with a solventinlet 32 for distributing solvent to the plurality of nozzles. Thedistribution circuit 30 may comprise piping, for example metal piping,able to withstand the solvent injection pressures provided for in theinvention, but the distribution circuit may also be integrally formed inthe cover portion or other member. The nozzles 29 are preferablyprovided with a venturi-shaped orifice for accelerating the solvent andproducing a fine mist, the nozzles being distributed over the crosssection of the chamber so as to distribute the mist as evenly aspossible over the cross-sectional surface of the chamber. An injectionsystem 34 may also be provided at the bottom end of the extractionchamber, for example fixed to the lower cover portion 20 and connectedto an inlet 36 interconnected to a conduit 38 through which pressurizedsolvent flows.

[0027] The lower injection system 34 serves in particular to enable ablast of pressurized solvent or gas to be injected from the bottom toagitate the raw material 24 between extraction passes, or at anintermediate stage during extraction. The blast injection serves todisturb and resettle the raw material 24 in order to prevent a channelor channels of low resistance forming through the raw material duringextraction, which reduce the extraction efficacy. Considering thepurpose of the lower injection system 36, it is also possible to connectthe inlet 36 thereof to a pressurized gas source other than the solventcircuit of the apparatus.

[0028] At the bottom of the extraction chamber, a further sieve orfilter may be provided to retain loose particles of material that mayhave passed through the sieve 26. The filter 39 may advantageouslycomprise a molecular sieve that retains or absorbs condensates, thefilter 39 being replaced or removed for drying at regular intervals, forexample after one or a certain number of extraction passes. Solvent andextracted oils and fats exit the extraction chamber through an outlet 40of significantly smaller cross section than the extraction chamber inorder to accelerate the solvent with its mixed and dissolved oils andfats.

[0029] Referring to FIGS. 3a and 3 b, the oil collection chamber 4comprises a casing 41 defining a chamber therein connected at one end tothe extraction chamber via an inlet conduit 42 and to a low pressureportion 15 of the solvent circuit via an outlet 43 separated from theinlet by one or a plurality of baffles 45 designed to collect theextracted oils and oil fats and resins, and prevent particles thereoffrom being aspirated into the low pressure solvent circuit portion.Extracted oils collecting at the bottom of the collection chamber may beremoved via a drain 44 whose opening is controlled by a tap or valve 46(as best seen in FIG. 1).

[0030] The baffle plates may be provided with curved shapes, generallyconvex for baffle plates with drain holes 48 near the outercircumference, and generally concave for the baffle plate having drainholes near the centre, the concave or convex shape being defined on theoil solvent receiving side thereof. The convex baffles 49 assist insolvent extraction by causing oil droplets projected thereon to spreadand flow across the baffle while solvent gas flows thereover. Theconcave baffles help to collect the oil and prevent droplets from beingaspirated into the recovery pump system.

[0031] In a procedure for extracting lipids and lipid soluble elements(“oils”), the extraction chamber 2 is first loaded with raw oil bearingmaterial and the top cover portion (18) is subsequently sealingly closedto the casing portion 22. A valve 52 (see FIG. 1) controlling thesolvent inlet 32 of the extraction chamber is in a closed position whilethe pumping system 6, which may comprise one or more pumps, feeds andpressurizes solvent in the solvent tank 12 and in the high pressurecircuit portion 17 that leads to the extraction chamber inlet 32.

[0032] On the low pressure circuit portion 15, a strong vacuum isproduced, drawing air out of the extraction chamber 2, the collectionchamber 4, and the vacuum tank 8. The vacuum tank 8 is particularlyadvantageous in that it helps to generate and maintain a strongervacuum, especially in the initial extraction phase when the extractionchamber inlet valve 52 is opened. For this purpose, the vacuum chamberpreferably has at least double the volume of the extraction chamber, butmore advantageously around three or more times the volume of theextraction chamber.

[0033] The pressure of solvent is at least at a pressure required tomaintain the solvent in its liquid phase around ambient temperature. Theoptimal operating pressure however may also be adjusted to take accountof the volume and density of raw oil bearing material in the extractionchamber.

[0034] Another consideration is the increased cost and complexity of theapparatus as pressures increase, whereby, in order to provide arelatively economical and effective extraction process, it isadvantageous to operate within a pressure range of one to five bars,although significantly greater pressures could be employed if needed,without departing from the scope of the invention.

[0035] One of the preferred solvents for use in the process according tothis invention, is high purity (for example 99.99% purity), isobutaneunder approximately 2.5 bars pressure in the high pressure circuitportion. After pressurizing the high pressure circuit portion anddepressurizing the low pressure circuit portion, the inlet valve 52 isopened. The pressure differential causes the solvent to acceleratethrough the nozzle 29 of the injection system 28 and a fine solvent mistis generated. The mist sprayed out of the nozzles 29 is drawn throughthe raw oil bearing material 24, through the sieves and filters 26, 39and exits through the outlet 40 into the collection chamber 4.

[0036] The acceleration of solvent through the nozzles 29, whichpreferably have a venturi shaped orifices, and the subsequent partialliquid to gas transformation of solvent mist sprayed out of the nozzles,creates a very rapid and significant adiabatic cooling that instantlyfreezes the raw material 24 as the solvent mist is forced by thepressure differential down through the extraction chamber. Withoutwishing to be bound by theory, the very rapid freezing of the oilsbearing raw material makes the oils more available to the solvent byfreezing aqueous and other non-lipid components. Furthermore, the flowof solvent mist and vapour washes the oils towards the outlet of theextraction chamber, preventing or significantly reducing the sticking orcollection of oils against the walls or parts of the extraction chamberand to the remaining fibres or meat of the raw material.

[0037] As the process according to this invention does not require thatall of the oils be dissolved in solvent, significantly lower quantitiesof solvent are required than in conventional solutions that requiresoaking of raw material and dissolving of oils for extraction with thesolvent. In plant and other living material, the rapid freezing not onlyhas the effect of retaining aqueous components, chlorophyll and fibres,but it is believed that the rupture of cells during the freezing processhelps to extract the oils. In addition, also considering that theprocess according to this invention does not require heating of theextracted oils to remove residual solvent (although a certain amount ofwarming could be provided if deemed useful) the high and low fractionsof oils are effectively extracted, thus providing the extracted oilswith a particularly rich olfactory profile and flavour. The freezingeffect and high yield extraction provided by the above-mentioned processis important in capturing volatiles and thermo-labile components in thisraw material, such components including ketones, esters and aldehydeswhich might otherwise be lost and/or destroyed in steam distillation orwhen other solvents are used with higher boiling points. Variousphytonutrients are also found in oils extracted with a process accordingto this invention.

[0038] In conventional processes, it is difficult to obtain for examplethe last five percent of higher turpines. These give the oils a tasteand olfactory profile which is unique in capturing the high notes aswell as the base notes of the original fresh material.

[0039] The solvent mist produced in the above-described process exhibitsa drop in temperature that may be in the range of −50 to −100° C.

[0040] A further significant advantage of this process is that it doesnot require any additional cooling system to chill the solvent and istherefore energy efficient compared to conventional cold solventextraction processes, also taking into consideration the lower volume ofsolvent required in the process according to this invention.

[0041] Furthermore, contrary to conventional extraction methods, sincethe raw material does not bathe in solvent, no flashing with other gasessuch as nitrogen is required at the end of the extraction process.

[0042] During the extraction process, the recovery pump station 6continues to maintain a strong vacuum by drawing the solvent gasesexiting the collection chamber 4 and subsequently pressurizing the gasesthat are transferred to the solvent tank 5 and/or to the overpressureand condensation tank 6, which may serve, on the one hand, as anoverpressure buffer of the high pressure circuit portion as well as atank for condensing the gaseous solvent. In order to improve thethermodynamic efficiency of the apparatus, a heat exchanger could beprovided between the extraction and oil conduction chambers 2, 4 on theone hand and the recovery pump system 6 and overpressure tank 10 on theother hand.

[0043] As the solvent and oil pass through the outlet extraction chamber40, the reduced section of the outlet accelerates and cools the mixtureand solution. This helps to separate off the solvent from the oilsbecause of its reduced solubility at lower temperatures. The vacuum inthe collection chamber 4 flashes off the solvent from the oils withoutthe need for any external heating of the extract which collects at thebottom of the extraction chamber after having passed the baffles. Theconvex baffles improve solvent removal and advantageously cause oildroplets to collect into larger drops and flow to the bottom of thecollection chamber, whereas the solvent gas flashed off the oil extractis sucked into the recovery pump station 6 and subsequently to the highpressure circuit portion.

[0044] It may be understood that the solvent that is used in thisinvention may be any organic compound that is a solvent for the desiredextract. It will usually be a gas under ambient conditions thatliquefies at a temperature in the range of −60° C. to 0° C. at ambientpressure. Other examples of suitable extractants for use in theinvention are hydrocarbon gases such as butane, propane and analogousgases with similar physical properties, or halocarbon variants such asfreons. The terms “hydrocarbon” and “halocarbon”, as used herein, do notexclude halohydrocarbons or indeed other substituents on carbon.Hydrocarbons and halocarbons are readily available and their use doesnot require that the extraction apparatus should withstand very highpressures, for example as required in carbon dioxide extraction.

[0045] Examples of raw materials that may be processed with theapparatus according to this invention include plants such as flowers,vegetables, fruits, seeds, and fish or other animal meats. In view ofthe rapid low temperature freezing effect, the raw material need not bedried and can be extracted either fresh or dried. When plants fromdifferent species are combined in the extraction chamber together to beextracted as one, the oils may undergo a reaction in the chamber andcombined to produce new molecules of a completely new oil. Withoutwishing to be bound by theory, the new oils may exhibit differentcrystal formations than either of the original oils and cannot beseparated into the original oils.

[0046] Other than the extraction of oils from living material theprocess according to this invention may also advantageously be used forremoving mineral oils from contaminated materials such as oil filters,sand, or soil, whereby the low solvent usage and energy efficientprocess according to this invention is particularly advantageous in suchapplications.

[0047] It may be noted that the relative simplicity of the extractionapparatus described above enables the apparatus to be easily scaled froma portable size, for example for field testing the properties ofcultivated plants, for example their ripeness or readiness to beharvested. The apparatus may also be made on a very large scale toreceive raw materials in the order of 10³ kg for large scale industrialextraction or decontamination.

[0048] It has been empirically found that using the process according tothis invention for many raw materials requires a proportion betweenroughly 4:1 and 2:1 quantities of solvent with respect to extracted oilin the first extraction run.

[0049] It will be understood that it is possible in the extractionprocess according to the invention to make more than one extraction runthrough raw oil bearing material in order to increase the yield, despitethe already high yield of the first extraction run.

[0050] The apparatus and process according to this invention also allowsfor the use of a second solvent or the addition of a modifier oradditive prior, during or subsequent the primary extraction process. Themodifier, second solvent, or additive may be supplied from an additionalchamber 56 (see FIG. 1) interconnected to the high pressure circuitportion 17 and to the extraction chamber 2.

[0051] It has been advantageously found that a small amount of 70 to100% pure ethanol in addition to a surfactant such as lecithin makescertain fats more available to the solvent such that the extraction runson some organic materials can be shortened. Moreover, some additionaloleoresins also become available if the proportions of the additive andprimary solvent are correctly balanced.

EXAMPLES

[0052] 1a) Control Process Using Conventional Extraction Process.

[0053] Raw material: chompalote, a dried and ground chile powder.

[0054] 823.25 grams of dried powder was extracted using a conventionalmethod: pump in gas and let it sit for one hour; pump out and recoveroils using 200° C. degree heat.

[0055] 89 grams of oil was recovered; the oil was dark red in colour,with good smell. A second soaking obtained 12 more grams of oil, whichwas lighter red in colour and with less smell after recovery.

[0056] A total of 101 grams of red oil was obtained using 10 litres ofliquid solvent (isobutane) each time (total 20 litres solvent).

[0057] 1 b) In Another Extraction Using a Process According to thisInvention:

[0058] 823.25 grams of raw and ground dried chile peppers wereextracted, starting at room temperature 24° C. for ten minutes usingfour litres of high purity solvent (isobutane) in super critical mistconditions to obtain 161 grams of a fine thick red oil with a superiorflavour and smell profile, well noted by all present.

[0059] This represents a substantial gain in yield and reduction in timespent during extraction. The superior flavour and odour profile are duepartly to gas recovery without using any heat, instead using the methodof drawing extracts with a strong vacuum, further providing bafflesurface areas in the collection chamber for the low temperature oil tocongregate on and allow for easy separation of gas from super criticaloils. Upper fine fractions disappear in methods using heat to recovergas to liquid state. Moreover, the use of high purity solvent (99.999%pure isobutane in particular) results in a more complete removal. Thetemperature in the extraction chamber during the extraction processvaried from about −40° C. to −90° C.

[0060] 3a) In another example, 1000 grams of cocoa nibs were extractedusing the conventional method mentioned in the first example.

[0061] 10 litres of liquid solvent were used in each cycle and 338 gramsof cocoa butter were extracted from two soakings and recoveries, eachsoaking and recovery process lasting approximately four hours. The cocoabutter was a mix of cocoa butter and white cake. 662 grams of cocoapowder were recovered as well.

[0062] 3b) In an extraction process according to the invention, onekilogram of cocoa powder was extracted to provide 523 grams of cocoabutter and cocoa white cake, and 477 grams of cocoa powder, in one step.This cocoa powder and cocoa butter and white cake have never reachedroom temperature during process which lasted 14 minutes at initial andambient room temperature and used four litres of solvent (isobutane).The temperature in the extraction chamber during the extraction processvaried from about −40° C. to −90° C.

[0063] 4a) In another extraction using Cassia bark 12 kilos wereextracted using the above mentioned conventional control method toobtain an oil yield of 0.89%. This is near the industry standard of 1%to 2% from this material depending on bark content and harvestconditions, 2% being the maximum yield hoped for using any conventionalmethod.

[0064] 4b) In a process according to this invention for extracting oilsfrom cassia bark, a 3.9% yield was obtained with a portion of the oilspontaneously crystallizing on contact with air. Both extractions (4aand 4b) were made from raw materials obtained from the same source atthe same time and divided.

[0065] 5) In another example, ginko leaves were extracted using aconventional method and a method according to the invention discussedabove. The conventional method resulted in a 1.6% yield whereas themethod according to this invention resulted in a 5.4% oil extract yield,with a percentage of ginkolic acid in the second extract that was 28%higher than in the control.

1. Process for solvent extraction of oils in oil bearing material, in anextraction chamber, comprising the formation of a solvent mist withsignificant adiabatic cooling, whereby a pressure difference between aninlet and an outlet of the extraction chamber drives the mist throughthe oil bearing material, the outlet being subjected to the action of avacuum.
 2. Process according to claim 1, wherein the solvent is suppliedto the extraction chamber inlet at a pressure exceeding atmosphericpressure.
 3. Process according the preceding claim, wherein the solventis supplied at the extraction chamber inlet at a pressure in the rangeof 2 to 5 bars.
 4. Process according to anyone of the preceding claims,wherein the outlet vacuum is generated by a gas recovery pump systeminterconnected to the outlet via an oil collection chamber.
 5. Processaccording to the preceding claim, wherein oils and solvent areaccelerated through a reduced section passage between the extractionchamber and an oil collection chamber.
 6. Process according to anyone ofthe preceding claims, wherein the solvent used is high purity isobutane.7. Process according to anyone of the preceding claims, including addinga second solvent prior to or during said solvent extraction process. 8.Process according to the preceding claim, wherein said second solventincludes ethanol and a surfactant.
 9. Process according to claim 7 or 8,wherein a surfactant is added to said second solvent.
 10. Processaccording to anyone of the preceding claims, comprising first and secondextraction runs.
 11. Apparatus for solvent extraction comprising anextraction chamber for receiving oil bearing material therein, saidextraction chamber comprising a solvent spray injection system connectedvia an inlet to a high pressure solvent feed circuit portion, saidextraction chamber connected via an outlet to a low pressure circuitportion connected to a gas recovery pump system.
 12. Apparatus accordingto the preceding claim, further comprising a vacuum tank interconnectedto the low pressure circuit portion, said vacuum tank having a volumeapproximately two times or more than the volume of the extractionchamber.
 13. Apparatus according to either one of the two precedingclaims, further comprising an oil collection chamber interconnected tothe extraction chamber via a reduced section passage.
 14. Apparatusaccording to the preceding claim, wherein the oil collection chambercomprises one or more baffles therein adapted to collect oil droplets.15. Apparatus according to the preceding claim, wherein at least onebaffle has a generally convex shape, as seen from the oil collectionside thereof.
 16. Apparatus according to anyone of the claims 11 to 15,wherein the extraction chamber further comprises a particle filter anddrier at the outlet thereof, adapted to retain particles and/or absorbaqueous condensates.
 17. Apparatus according to anyone of claims 11 to16, wherein said spray injection system comprises a solvent distributioncircuit and a plurality of venturi nozzles adapted to spray asubstantially evenly distributed solvent mist across the cross sectionof the extraction chamber.
 18. Apparatus according to anyone of claims10 to 15, wherein the extraction chamber comprises a blast nozzle systemat a lower end of said extraction chamber for injecting gas or a solventmist at a bottom end of the oil bearing raw material.